The invention relates to compositions for the preparation of polymeric gels, the polymeric gels and their uses, and more particularly to a composition including adequate proportions of certain polymers, aldehydes and amines to form a polymeric gel. Such polymeric gels with appropriate gelation times are useful for reducing or eliminating the flow of water through surfaces and earthen formations, as adhesives and for the formation of fibers, filaments, films and membranes; and in soil stabilization.
A primary utilization of gels in accordance with this invention is the reduction of water infiltration in structures such as tunnels, sewer lines, or the like. The name commonly given to such a material is "grout". A variety of compositions have been utilized for this purpose. Mixtures of acrylamide and N,N'methylenebisacrylamide have been commonly used for controlling water infiltration into these structures over the past twenty years. Such mixtures are usually injected in the form of an aqueous solution into the earthen formation adjacent to the tunnel, well, sewer lines, and the like along with a catalyst which, after a short period of time, causes these vinyl type monomers to polymerize. The result is a fragile gel-like material containing 80 to 95% water which, in effect, stops or reduces water infiltration. The process is described, in part, in several U.S. patents such as U.S. Pat. Nos. 2,801,983, 2,940,729, 3,223,163, and 4,094,150. Certain disadvantages of the process have been recognized in the art, including the toxicity of the monomers, the fragile nature of the resultant gel, and poor adhesive qualities. The toxicity of the monomers becomes a problem through unavoidable handling practices, spills and through contamination of ground water caused by incomplete polymerization.
More recent art (U.S. Pat. No. 4,155,405) has shown that polyacrylamide with a molecular weight of at least two million will react with dialdehydes to form gels in not less than 24 hours at pH values of about 6.5 to 8.5. When the pH is increased, gels with set times in the order of 10-15 minutes are formed. Such gels, however, are ultimately unstable.
Gel set time is a very important parameter for many applications of grout and very often the only parameter used to characterize gels. It is often desirable to have a gel form and become rigid in times as short as a few seconds. In other applications, a preferred time might be several minutes. For example, in the sewer grouting process, it is desirable to have gel times of 15 to 60 seconds thereby reducing the cost per mile of treating the sewer. If the gel does not form and achieve adequate strength quickly (i.e., have a short gel time), there is danger of the material being expelled or washed away by the hydrostatic head of ground water when the injection equipment is moved. Some gel forming compositions cannot be adjusted to give desirable ranges of set times under the different conditions encountered in the particular application. Such conditions include summer and winter temperatures, sunlight which can trigger premature gelation, and dilution by ground water. Some compositions produce fragile gels whose sealing action fails when the earth around the structure shifts. Other compositions produce gels which have poor adhesion to the structure or surrounding formation or which, as indicated above, are unstable.
Accordingly, there exists a need in the art for a polymeric gel that is formed from nontoxic materials, that has a wide range of set times, that has good adhesion to common structural materials, that is stable and that is tough and yet plastic. It is an object of my invention to provide novel polymeric gels which satisfy this need. Other objects and advantages of the invention will be apparent from the following description.